The present invention relates to implantable devices and, more particularly to an implantable orthopedic support and a method for making the support.
Various joints in animals, such as humans, are defined by a fibrocartilaginous disc interposed between articulating bony surfaces. Joints may be classified according to the amount of movement they permit. Moveable joints may permit relative movement between the adjoining bones in several ways: gliding, angular, circumduction, and/or rotation. Joints, because of their location and constant use, are prone to stress, which may result in injuries. A common injury occurs to the fibrocartilaginous disc interconnecting two articulating bony surfaces. The fibrocartilaginous disc also may degenerate over time. By way of illustration, two fibrocartilage discs of particular interest include intervertebral discs and menisci of knee joints.
A human intervertebral disc is located between the endplates of adjacent vertebrae to stabilize the spine, distribute forces between vertebrae and cushion vertebral bodies. The intervertebral disc employs various modes of articulation that provide for changing the instant center of rotation of adjacent vertebral surfaces relative to one another and permit lateral-to-lateral and anteroposterior translation of vertebrae relative to one another.
Spinal discs may be displaced or damaged due to trauma, disease or aging. One common condition, which is referred to as a herniated or ruptured disc, occurs when the annulus fibrous allows the nucleus pulposus to protrude into the vertebral canal. The protruding nucleus pulposus may press on the spinal nerve, which may result in nerve damage, pain, numbness, muscle weakness and paralysis. Intervertebral discs may also deteriorate due to the normal aging process or disease. As a disc dehydrates and hardens, the disc space height will be reduced, which may lead to instability of the spine, pain and decreased mobility.
Sometimes the only relief from the symptoms of these conditions is discectomy, or surgical removal of a portion or all of an intervertebral disc followed by fusion of the adjacent vertebrae. When a disc is removed, a space is formed, which if left untreated, may allow the disc space to collapse. In addition to severe pain, a collapse of the disc space may cause instability of the spine, abnormal joint mechanics, premature development of arthritis and/or nerve damage.
An undamaged meniscus of a knee joint provides shock absorption for the knee by ensuring proper force distribution, stabilization, and lubrication for the interacting bone surfaces within the knee joint. Much of the shock absorbing function of the medial and lateral menisci is derived from the elastic properties inherent to cartilage. When a meniscus is damaged, such as through injury, disease, or inflammation, arthritic changes occur in the knee joint, which may result in a loss of function and/or pain.
Since joint cartilage in adults does not naturally regenerate to a significant degree once it is destroyed, damaged adult menisci have historically been treated by a variety of surgical interventions including removal and replacement with prosthetic devices. In one respect, a meniscus prosthesis may be utilized. Examples of meniscus prostheses may be formed of resilient materials, such as silicone rubber or natural rubber, collagen, tendon, or fibrocartilage. By way of further illustration, a meniscus heterograft has been proposed to replace a damaged human meniscus.
The present invention relates to an implantable support apparatus for cushioning between articulating structures, such as bone or other tissue. The apparatus includes a plurality of sheets of a substantially biocompatible tissue, which are connected together to form a laminated stack of the tissue. In accordance with one particular aspect, each sheet in the stack is treated animal pericardium.
The shape of the laminated stack is determined from the shape and configuration of each of the plurality of sheets that comprise the stack. The stack may be dimensioned and configured according to the particular use in which it is to be employed. For example, the stack may be kidney shaped, circular, annular, or other shapes and may include one ore more apertures extending through the stack to help provide a desired level of cushioning.
One aspect of the present invention provides an implantable orthopedic support apparatus. The apparatus includes a plurality of generally flat sheets of a flexible tissue material. The plurality of sheets are connected together so as to inhibit movement between adjacent sheets.
According to one particular aspect, each of the sheets may be dimensioned and configured according to the dimensions and configuration of human vertebrae, such that the apparatus provides an intervertebral disc prosthesis. According to another aspect, one or more apertures may extend through the plurality of sheets and the apparatus may be dimensioned, such that it may be utilized to replace a meniscus (or menisci) of a knee joint.
Yet another aspect provides an implantable orthopedic support apparatus. The apparatus includes a molded and cross-linked protein structure having a pair of surfaces for engaging a respective articulating structure when implanted. The molded and cross-linked protein structure is detoxified to mitigate calcification.
Another aspect of the present invention provides a method of manufacturing an implantable orthopedic support apparatus. The method includes forming a plurality of similarly dimensioned and configured sheets from a flexible biocompatible material and axially aligning the plurality of sheets to form a stack of the plurality of sheets. The stack of sheets is secured together so as to mitigate shearing between adjacent sheets.
Still another aspect of the present invention provides a method of manufacturing an implantable orthopedic support apparatus. The method includes molding a protein material into a desired shape having a opposed sides dimensioned and configured for engaging respective articulating structures of a patient. The molded protein material is cross-linked and substantially detoxified to form the implantable orthopedic support apparatus. As a result, after the support apparatus is implanted, the support apparatus provides shock-absorbing properties between respective articulating structures of the patient and mitigates calcification of the implanted prosthesis.